JUDY WOODRUFF: Next, Most of the country is experiencing a warmer-than-usual springtime, with temperatures hitting summertime levels.
Here in the nation's capital, that's causing the famous cherry blossoms to arrive early for the celebration of a 100-year-old tradition.
Hari Sreenivasan has our story.
HARI SREENIVASAN: The Eidson family from Arlington Heights, Ill., was in Washington, D.C., this weekend for a family reunion. And they lucked in to an earlier-than-normal cherry blossom season.
BILL EIDSON, resident of Illinois: I was following it on the Internet. And I was hoping and hoping that we'd be having an early bloom this year with the mild weather. And sure enough, we have gotten lucky with that.
KELLY EIDSON, resident of Illinois: It's something I have always tried to make it down here in the spring. It just this is the first time it's happened in like 10 years that we have made it.
HARI SREENIVASAN: These blossoms are only around for about two weeks on average. And predicting when those two weeks are going to happen is the job of the National Park Service. Due to mild winter in the D.C. area, the Park Service already moved this year's projected peak bloom dates earlier twice.
WOMAN: Aren't they gorgeous?
HARI SREENIVASAN: It now says 70 percent of the cherry trees here will be blooming in the next two days.
Bill Line is a spokesman for the National Park Service.
BILL LINE, spokesman, National Park Service: It's much warmer this year than what it has been, and the trees are simply reacting to the temperatures.
HARI SREENIVASAN: Cherry trees are very sensitive to temperature, not just how hot it is getting during the day, but also how cold it gets at night.
BILL LINE: It's typical this time of year in March to still have, oh, you know, 30, 32, 34 degrees as the overnight low temperature. This year, we have had a number of days, multiple days, where the coldest it gets overnight is 50 degrees, 55 degrees. A couple of days, we had the overnight low was 60 degrees.
HARI SREENIVASAN: Wow.
BILL LINE: So, that's a significant change in terms of that overnight low temperature.
HARI SREENIVASAN: In fact, the cherry trees here in the Tidal Basin have bloomed almost a month later some years. We know that because the Park Service has been keeping data on these special trees for decades. They were a gift from Japan 100 years ago this year.
And it's become synonymous with spring in Washington, D.C. Now the annual Cherry Blossom Festival attracts more than a million visitors and is expected to bring in more than $100 million to the local economy. Whether this year's extraordinarily early bloom is due to climate change or just an unusual streak of warm weather across the country, studying peak bloom times over a longer period reveals something interesting.
Dr. Soo-Hyung Kim studies how plants adapt to environmental factors at the University of Washington. He's been poring over 50 to 60 years of dates when cherry trees have bloomed at this famous landmark and says the blooming is indeed tied to rising temperatures.
DR. SOO-HYUNG KIM, University of Washington: Every degree of temperature that you add can have quite an impact on their process of flowering.
HARI SREENIVASAN: Over the past 60 years, on average, the cherry trees in Washington, D.C., are reaching their peak bloom earlier, by about five days.
Still, predicting when the cherries will bloom next year is almost impossible. But based on two scenarios of population and climate devised by the Intergovernmental Panel on Climate Change, Dr. Kim predicts that decades from now cherry blossoms will steadily arrive earlier.
He says, in one scenario, the cherries could come between five and 13 days earlier by the 2050s. In another scenario, the trees could bloom between 10 and 29 days earlier by the 2080s, meaning a peak bloom in late February.
So, while these trees and the festival that accompanies them add millions in tourism dollars, there's still no guarantee that the people and the blossoms will arrive at the same time.
BILL LINE: People have to plan ahead. People make those hotel and plane reservations in advance. And Mother Nature is what Mother Nature is.
HARI SREENIVASAN: If you're in luck, like the Eidsons, you get to see a fabled change of seasons.
BILL EIDSON: I think it's an iconic part of Washington, D.C., that we've all heard about for -- growing up and you always see pictures of it. And it's great to have a chance to really see it and be a part of it.
HARI SREENIVASAN: But, if you're making plans to see the cherry trees in full bloom, over the next few decades, it might make sense to err on the earlier side.
JEFFREY BROWN: Online, we have another climate-related story, marking the beginning of a special NewsHour series called Coping with Climate Change. It's about a man dealing with the Texas drought by collecting, bottling and selling rainwater. He calls it Cloud Juice.